Sheet stack advance mechanism



July 18, 1961 R. R. TARBUCK ETAL 2,992,820

SHEET STACK ADVANCE MECHANISM 2 Sheets-Sheet 1 Filed Dec. 21, 1959 a INVENTORS ROBERT R. TARBUCK THOMAS J. M KNIGHT ATTORNEY July 18, 1961 R. R. TARBUCK ETAL 2,992,820

SHEET STACK ADVANCE MECHANISM 2 Sheets-Sheet 2 Filed Dec. 21, 1959 INVENTORS ROBERT R. TARBUCK BY THOMAS J. M KNIGHT ATTORNEY machine.

United States Patent 2,992,820 SHEET STACK ADVANCE MECHANISM Robert R. Tarbuck, West Chester, and Thomas J.

McKnight, Paoli, Pa., assignors to Burroughs Corporation, Detroit, Mich., a corporation of Michigan Filed Dec. 21, 1959, Ser. No. 860,829 9 Claims. (Cl. 271-39) This invention relates generally to sheet feeding systems and more particularly to apparatus for advancing a stack of sheet-like articles to a delivery station, and to a feeding device at the delivery station for separating sheets individually and successively from the stack.

The principal object of the present invention is to provide an improved sheet feeding mechanism for feeding sheets individually and successively from a stack of sheets with utmost accuracy and reliability.

Another object of the invention is to provide such a mechanism for a sheet feeding system utilizing a friction sheet feeding device whereby the feeding device is maintained against the sheet stack within a predetermined constant force range throughout the entire feeding run, so that each sheet is fed from the stack with substantially the same degree of force.

A further object of the invention is to provide a sheet feeding mechanism having instrumentalities responsive to changes in position of a movable friction sheet feeding device for regulating a sheet stack drive means thereby to maintain the sheet feeding device in pressing contact with the sheet stack within a predetermined constant force range.

In accordance with the above objects and considered first in its broad aspects, the invention comprises apparatus for advancing a stack of sheets and a sheet feeding device which is moved by the advancing sheet stack. Instrumentalities are incorporated which respond at a predetermined limit of such movement of the sheet feeding device for stopping the advancement of the sheet stack. As sheets are separated from the stack by the sheet feeding device the latter moves in a different direction to a predetermined limit at which time such movement actuates the above instrumentalities to resume advancement of the sheet stack.

The invention will be more fully understood when the following detailed description of a specific embodiment thereof is read in conjunction with the accompanying drawings in which:

FIG. 1 illustrates a sheet feeding machine constructed in accordance with the invention;

FIG. 2 is a sectional view taken on line 2-2 of FIG. 1 showing certain details of a sheet stack pusher;

FIG. 3 is a sectional view of a sheet feeding unit and rockable frame therefor taken on line 3-3 of FIG. 1;

FIG. 4 is a sectional view of a spring clutch taken on line 4-4 of FIG. 1;

FIG. 5 is a view looking in the direction of arrows 55 of FIG. 1 showing an electromagnetic detent mechanism for controlling the operation of the spring clutch; and

FIG. 6 is a diagram of control circuitry for illustrating one particular method of operation of the sheet feeding machine.

Referring to the drawings, it is seen that the preferred embodiment of the invention incorporates a sheet feeding device 10 (FIG. 1) having a rockable frame 12. Frame 12 comprises spaced-apart rock levers 14 and 16 (FIG. 3) pivotally mounted at their lower regions on bearings 18 and 20 secured in the base 22 of the ma- A shaft 24 is journalled for rotation in bearings 18 and 20 and is rotated from a suitable source of power such as a motor M1. Between the upper portions of rock levers 14 and 16 is a sheet feeding unit or feed 2,992,820 Patented July 18, 1961 roller 26 secured on a shaft 28 which is journalled for rotation in bearings 30 and 32 secured respectively in the rock levers 16 and 14. The feed roller 26 is rotated by means of a belt 34 which passes around pulleys 36 and 38 fixed respectively on shafts 24 and 28. A roller 40 secured on shaft 24 forwards the sheets to their destination as they are separated from a sheet stack S (FIG. 1) by the feed roller 26.

The rollers 26 and 40 extend through apertures in a sheet metal guide member 42 secured to the upper ends of the rock levers 14 and 16 and having flanges 42a and 42b secured to the lower portion of the rock levers. Guide member 42 extends below roller 40 to form a delivery chute with a fixed guide member 43.

On the rock lever 14 is an actuating arm 44 adapted for operating a feed switch 46 and a safety switch 48. Secured to the lower extremity of rock lever 14 is a tension spring 50, preferably adjustable by means of a screw 52, for pressing the feed roller 26 against the stack S with a predetermined amount of force.

Extending upwardly from base 22 are spaced-apart members 51 and 53 which together with a stack support or table 54 comprise a hopper 55 for the stack of sheets S. The table 54 is secured to base 22 and constructed of elongated members 54a and 54b which are spaced apart throughout their length to provide a slot 56 for guiding a stack pusher 58. The pusher 5 8 comprises an interior body 60 secured to and substantially surrounded by a shell 62 of sheet metal construction. The lower extremities of the left and right walls 62a and 62b of the shell 62 are each formed with a depending key portion 620 which extend freely through the slot 56. Below table 54 and extending from the key portions 620 are T-shaped lugs 62d and 62e which are bent inwardly toward each other to slidably secure the stack pusher 58 to the table .54.

A lever 64 is pivotally mounted at one end 66 to the body 60 and has its opposite end 68 with an integral depending sector nut 70. The lower edge portion of lever 64 is formed with a locking notch 72 adapted to receive a pin 74 mounted on the lower end of a hand lever 76 rockably mounted on a pin 78 secured to the body 60, the hand lever 76 extending through an aperture 80 in the shell 62. The sector nut 70 is biased downwardly into threaded engagement with a lead screw 82 by means of a compression spring 84 and is stopped in this position when lever 64 comes against pin 74. An anti-friction roller 86 extends slightly through an aperture in shell 62 and is mounted for free rotation on a shaft 88 secured to body 60.

The drive for the stack pusher 58 includes the lead screw 82 which is journalled for rotation in the base 22 of the machine in bearings 90 and 94. The lead screw 82 is coupled to a reduction worm gear drive 96 by means of a modified spring clutch 98 of well known construction, the worm 100 being rotated by a motor M2.

The spring clutch 98 (FIG. 4) comprises an outer sleeve or barrel 102', and input and output sleeves 104 and 106 respectively, which are freely received in the barrel. The input sleeve 104 is secured to or integral with the worm wheel 108 and freely mounted on the lead screw 82 wln'le the output sleeve 106 is secured to the lead screw. A right-hand helical spring 110 surrounds shank portions 112 and 114 of the input sleeve 104 and output sleeve 106, and has one of its ends anchored in a hole 116 in the output sleeve 106 and its other end anchored in a hole 118 in barrel 102. A toothed wheel 120 in the form of a ratchet is secured on or made a part of the barrel 102.

Associated with wheel 120 is an electromagnet (FIG. 5) in circuit with the feed switch 46 and safety switch 48. The electromagnet 1 22 is secured to a fixed frame 124 to which is pivotally mounted at 126 a detent or armature 128. A tension spring 130 connected to one end 13 2 of armature 128 and to a lug 134 extending from frame 124 biases the armature toward the wheel 120.

The operation proceeds as follows: Hand lever 76 is pulled or rocked clockwise until pin 74 engages in notch 72 to lock the sector nut 70 in an upward position out of engagement with the lead screw 82, and the stack pusher 58 is retracted rightw'ardly to a convenient loading position. A stack of sheets S is placed in the hopper 55 on table 54 and hand lever 76- pressed leftwardly or rocked counterclockwise until it abuts the leftward edge 80a of aperture 80. Continued pressure on the hand lever serves to move the stack 5 which is thereby advanced toward the feed roller 26. This movement of hand lever 76 allows the sector nut 70 to momentarily engage the lead screw 82 as the pin 74 leaves the notch 72. However, as pin 74 moves rightwardly past the vertical centerline of pin 78 it rocks lever 64 upwardly to disengage the sec tor nut 70 from lead screw 82 and holds it upwardly while the sheet stack S is being pushed toward the feed roller 26.

When the sheet stack has been moved to within a short distance of feed roller 26, the hand lever 76 is released thus allowing the sector nut 70 to engage the lead screw 82. A stack drive switch 136 (FIG. 6) is then closed to complete a circuit to motor M2 for rotating the lead screw. Closing of switch 136 also serves to energize electromagnet '122 which then attracts and holds armature 128 away from wheel 120. With wheel 120 free of armature 128 the rotation of the input sleeve 104 causes spring 110 to wrap tightly about the shank portions 112 and 114 thereby transmitting rotation to the lead screw 82 for advancing the sheet stack.

As the sheet stack advances it presses against the feed roller 26 and rocks the frame 12 in a counterclockwise direction on bearings 18 and 20 until the actuating arm 44 transfers or opens the switch 46. Opening of switch 46 de-energizes electromagnet 122 to allow armature 128 to engage in a tooth of wheel 120 thus to stop wheel 120 from rotating. This has the effect of giving the spring 110 an unwinding movement to uncouple the output sleeve 106 from the input sleeve 104. The input sleeve 104 will then continue rotating freely on the lead screw 82 while the output sleeve 106 and lead screw will stop rotating thus stopping advancement of the sheet stack S.

At the same time that the feed switch 46 transfers, the feed roller 26 will be near the maximum limit of a predetermined preferred force range established by the tension of spring 50 and the position of the switch 46 so that sheets can then be separated from the stack with a predetermined force. A switch 138 (FIG. 6) is then operated to close the circuit to motor M1 to rotate the feed roller 26 for feeding sheets from the stack. As sheets are fed from the stack, frame 12 will gradually rock clockwise, as urged by spring 50, until switch 46 transfers to close its contacts, at which time feed roller 26 will be near the minimum limit of the preferred force range. Closing of switch 46 contacts will energize electromagnet 122 to withdraw the detent or armature 128 from wheel 120 to again free the spring clutch 98 and allow lead screw 82 to resume rotation and advancement of the sheet stack until switch 46 again transfers to stop advancement of the sheet stack as described above. The operation thus continues automatically until all sheets have been fed from the hopper.

When the last sheet has been fed from the hopper by the feed roller 26, the feed roller will then contact and rotate the anti-friction roller 86. In this manner, sliding friction between the feed roller 26 and stack pusher 58 which would normally be encountered at this time in other devices, is accordingly here eliminated.

It can now be seen that the sheet feeding device 4 will be oscillating back and forth during a sheet feeding run, and within the preset force range established by tension spring 50 and the position of feed switch 46, so that each sheet in the stack will be separated from the stack with substantially the same degree of force. It is understood, of course, that the feed switch 46 has an operating range, that is, its contacts will make and break at different points, in a manner well known.

If the feed switch 46 fails to effect stopping of the stack pusher 58 the safety switch 48 will be operated by the actuating arm 44 to open its contacts and shut down motors M1 and M2 before the maximum limit of the pre: ferred force range is exceeded. An additional safety feature is embodied in the arrangement of the sector nut 70 to guard against the possibility of the safety switch 48 failing to operate. In such case, if the apparatus should jam such as to bring the stack pusher 58 to a halt, continued rotation of lead screw 82 will force the sector nut 70 upwardly out of engagement with it, thus disconnecting the stack pusher 58 from the drive.

While there has been disclosed a specific embodiment of the invention, it is understood that the invention may be constructed in a variety of sizes, shapes and arrangements without departing from its true spirit and scope. Accordingly, the invention is not to be limited by the specific device disclosed but only by the subjoined claims.

, What is claimed is:

1. A sheet stack advancing mechanism comprising, a movable sheet feeding device, a pusher for advancing a stack of sheets against said sheet feeding device causing the latter to move, means for driving said pusher, and means operable by said sheet feeding device at 'a predetermined limit of movement thereof for stopping said pusher.

2. A sheet stack advancing mechanism comprising, a frame, a pivotal mounting for said frame, a sheet feeding unit carried by said frame, a pusher for advancing a stack of sheets against said sheet feeding unit causing the latter to rock said frame on said pivotal mounting, means for driving said pusher, and means responsive to said rocking of said frame at a predetermined limit thereof for stopping said pusher.

3. Apparatus for advancing a stack of sheet-like articles comprising, a sheet feeding device, a pusher for advancing a stack of sheets against said sheet feeding device caus ing the latter to move, drive means for said pusher, releasable means coupling said pusher to said drive means, and means responsive to said movement of said sheet feed-. ing device at a predetermined limit of movement thereof for stopping said pusher.

4. A sheet stack advancing mechanism comprising, a sheet feeding device, pusher means for advancing a stack of sheets against said sheet feeding device causing the latter to move, drive means for said pusher means, a rotatable transmission member coupling said pusher means to said drive means, and means responsive to said movement of said sheet feeding device forstopping rotation of said rotatable transmission member while said drive means continues operating.

5. The combination comprising a stack pusher, drive means, a lead screw rotatable by said drive means, and'a sector nut yieldably coupling said lead screw to said stack pusher, said sector nut being releasable to allow said stack pusher to be moved independently of said drive means. v

6. A combination according to claim 5 characterized further in that said sector nut is constructed so as to release automatically for uncoupling said stack pusher from said lead screw whenever said stack pusher is stopped by a jam while said drive means is operating. Y 7. The combination comprising, a rotatable friction: sheet feeding unit, a pusher for advancing a supply of for the removal by the latter of individual sheets from said supply, and a roller carried by said pusher and operative upon the removal of the last sheet from said supply to be rotated by said friction sheet feeding unit and to prevent the latter from coming in contact with said pusher.

8. Apparatus for controlling the advancement of a supply of sheets comprising, a frame, means for pivotally mounting said frame, a rotatable sheet feeding unit carried by said frame, means for rotating said sheet feeding unit, a pusher for advancing a supply of sheets against said sheet feeding unit causing said frame to rock on said pivotal mounting, means urging said frame to rock in the opposite direction as sheets are fed from said supply by said sheet feeding unit, drive means, a lead screw rotatable by said drive means, a sector nut coupling said pusher to said lead screw and being releasable to allow said pusher to be moved independently of said drive means, and means responsive at predetermined limits of said rocking movements of said frame for controlling rotation of said lead screw.

9. Sheet feeding apparatus comprising, a hopper for supporting a stack of sheets, a stack pusher for advancing said stack of sheets through said hopper toward one end thereof, means for so operating said stack pusher, a

sheet feeding device, means for operating said device to 25 remove sheets successively from said stack, means mounting said sheet feeding device at said one end of said hopper in the path of movement of said stack of sheets, said mounting means permitting movement of said sheet feeding device in the direction of advance of said sheet stack in response to pressure of said sheet stack against said sheet feeding device, resilient means biasing said sheet feeding device in the opposite direction by a force which increases to a predetermined maximum as said sheet feeding device is moved by said sheet stack, and control means in the path of movement of said sheet feeding device and actuated by said sheet feeding device when said increasing force is near its predetermined maximum to disable said stack pusher operating means to stop the advance of said sheet stack whereby said resilient means is eflfective to urge said sheet feeding device in the opposite direction against said sheet stack while sheets are removed from said sheet stack by said sheet feeding device, said control means being responsive when a predetermined minimum force is nearly reached in said resilient means while the latter is urging said sheet feeding device in said opposite direction to reactivate said stack pusher operating means.

References Cited in the file of this patent UNITED STATES PATENTS 

